Changing disciplines after finishing undergrad Degree

I am a Chemical engineering student with pretty good grades, and about finish my undergraduate degree. I am 100% sure i want to go to grad school, but recently i am starting to get interested in other disciplines.

My question is, how difficult it is for someone with my background to change discipline to something like mechanical engineering, aerospace engineering or applied physics?

honestly, it depends on the project! If you see a project that interests you in a different school, then you go for it. My research group (materials engineering) has physicists and chemists graduates in it too. I almost when from materials to chemical engineering, because i was interested in the project offered.

My supervisor is keen on having a spectrum of disciplines in the group because it allows students to support each other and diversify in skills. Other supervisors I know do this also.